The device of the present invention directly derives and complements several inventions owned by applicant, the first configuration having been filed with Brazilian Patent Office Aug. 21, 1978 (PI 7805402-8), the second one on Sep. 9, 1985 (PI 8504326-5), the third one on Feb. 2, 1991 (PI 9100456-0), the fourth one on Nov. 5, 1993 (PI 9304495-0), the fifth one on Mar. 27, 1996 (PI 9601145-9), the sixth one on Mar. 23, 2009 (PI 0902183-3), and the last one on Jun. 20, 2016 (BR102016014526-0).
The first configuration (basic structure) is defined by parts 1—Upper/Lower Chord, parts 11—Diagonals of a Frame, parts 12—Bridging angles of the Frame, parts 15—Roof Coils (tiles), parts 8—Cover plate (See, FIG. 1A).
From its launch to the present days, the system initially revealed, described above, has about 10 million square meters installed, meeting all the demands and technical requirements requested by the market.
However, there have been changes in the needs imposed by the coverage market, which requires product adaptation. Thus, nowadays, the product is often used for purposes or in conditions different from those used as a basis for its development. One of the changes concerns the overload imposed on the coverage, that is, there is a need today to use this coverage system with a payload greater than the one initially assigned to the coverage. The coverage of a mall, for example, should support loads of plaster lining, electricity pipe rack, sprinkler distribution network, sound reinforcement network, air conditioning etc.
As a result, the structure is limited by the capacity of the connections between its parts. In the case of the initially disclosed system, its structure is composed of lattice girder beams, with bolted connections between the parts: chord (1) and diagonal (11).
For the sizing of these connections, the resistance of a screw to cutting (FIG. 5A), the crushing of a hole (FIG. 5B) and longitudinal (FIG. 5C) and transverse tears of the connected plates are considered.
To increase the resistance of the bolt to cutting one can use special steel alloys or increase a diameter of the bolt.
In the case of a sheet metal, the increase in its resistance to the cited effects—crushing of hole or tears—is due to the increase in its thickness, which causes the entire piece to be very heavy, increasing the cost as a whole. The increase in thickness does not apply to parts or sections of the plate, but to its full extent, making it impracticable to reinforce this or that point increasing the thickness.